JPS59124769A - Semicondutor device - Google Patents

Abstract

PURPOSE:To obtain a high electron mobility transistor with a Schottky electrode, electrostatic capacitance between gate-sources thereof is small, cut-off frequency thereof is high, high-frequency characteristics thereof are excellent and gate dielectric strength thereof is large. CONSTITUTION:An un-doped layer 31 in three layers constituting an electron supply layer 3 has a function preventing ionic scattering. A high-concentration N type layer 32 satisfies conditions in which a two-dimensional electronic gas having surface concentration of approximately 10<11>/cm<2> or more necessary and sufficent as a conductive medium of the semiconductor device is generated, but its thickness is very thin. The third, an n type layer 33 as an uppermost layer satisfies conditions necessary and sufficient for allowing the formation of a depletion layer to the lower section of a gate electrode, and has not thickness more than required. Consequently, the thickness of the electron supply layer 3 is sufficiently thin and electrostatic capacitance between the gate-source is reduced sufficiently, cut-off frequency is improved, and high-frequency characteristics are enhanced. Dielectric strength between the gate-sources is also improved because impurity concentration in the N type layer 33 has been reduced properly.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a semiconductor device, and particularly to a high electron mobility transistor having a Schottky electrode. More specifically, the present invention relates to improvements in such high electron mobility transistors that improve the cutoff frequency, which is one of the indicators of high frequency characteristics, and further improve the gate dielectric strength.

(2) Background of #technology and problems with conventional technology High electron mobility transistors have different electron affinities 2
A group of electrons (two-dimensional electron gas) that stays near one heterojunction surface formed by joining two types of semiconductors.
A control electrode is used to control the electron surface concentration of An active semiconductor device that controls energy dance.

The combination of the stranded semiconductors that make up the high-electron-momentum transistor and the flexibility of the 0-value semiconductors are: (a) their lattice constants are the same or close to each other; Because of the large size and the large difference in the θ gundo gap, there are many examples [2. These are listed in the previous patent issued by Ryoji Izuru (#Chomei No. 55-82035).

In addition, whether J- with a thick electron affinity is placed in the upper layer or the lower layer, through a unique winter crop,
Addition key I] High and low: It is possible to manufacture child mobility transistors.

Both the normally-on type and the normally-off type can be constructed by adding f to Wl with their own specific requirements. however,
The present invention is an improvement on the normally-on type.

A high electron mobility transistor is characterized in that the electron layer @T#1 of the above-mentioned retained electron group (two-dimensional electron gas) becomes extremely large, especially at a low temperature. (Thanks to Noto), it is characterized by high operating speed, making it suitable for high frequency applications.

2π C()S iday ■7, fr is the cutoff frequency I), Gm is the transfer conductance a) 1゜Oos 11
is the isocapacitance between source and source.

It is desirable to improve the cut-off frequency, which is expressed by
It is desirable to reduce source-to-source capacitance. On the other hand, since the dielectric strength of Schottky gates is not necessarily high, it is also desirable to improve this.

(3) Object of the Invention The object of the present invention is to provide a structure having a low static capacitance between the gate and the source, a high cut-off frequency, excellent cylindrical frequency characteristics, and a Schottky electrode with a large gate source breakdown strength. The objective is to provide a high electron $al'f) run raster.

(4) Structure of the Invention The above object is to eliminate a group of electrons (two-dimensional electron gas) as a conductive medium, and the impedance of a conductive path constituted by the conductive medium is controlled by a control electrode provided on either of the semiconductor double layers, and the conductive path is provided with the control electrode sandwiched therebetween. In a semiconductor device connected to a pair of input/output electrodes, the small layer of electrons and Japanese book among the # conductor layers constituting the semiconductor double layer is further divided into two layers. The layer that is in contact with the layer with high electron affinity is a thin layer containing a high concentration of n-type undesirable substances (1), and the layer that is not in contact with the layer with high electron affinity is the thin layer (1) with n-type with low concentration change. I), where φ is the surface potential of the small layer of the electronic condyle,
(al), q is the electron charge (1), ε is the dielectric constant of the layer with a large electron affinity (al), N is the n-type impurity concentration number of the layer with a long electron affinity), d is the thickness of the layer with the above electron affinity.

I) is achieved by satisfying the following. In particular, the substrate and electrons? The layer is gallium arsenide (GaAs)-r
(I) When the layer with low electron affinity is aluminum gallium arsenide (A/GaAs), it has particularly excellent properties. In order to generate a group of retained electrons (two-dimensional electron gas), one of the two types of semiconductors constituting one of the above-mentioned heterojunction surfaces is the smaller semiconductor layer (electron supply layer) in the electronic layer Japanese book. In addition, the presence of an electron source that is supplied to the interface is essential.

However, the surface # change n8 of the retained electron group (two-dimensional electron gas) is n ff of the above-mentioned layer with small electron affinity (electron supply #)
Jj is proportional to the square root of KND, and satisfies the relationship of 1β to ns, so in order to obtain a two-dimensional electron gas surface concentration of about IQ”/cm2, an n-type impurity of about 1018/σ3 is required. The thickness of the semiconductor layer with a concentration of 6 (1 (X:l) is sufficient.

However, Schottky small: Between the pole and the semiconductor, the formula φ is the surface potential tear I), q is the electronic charge (number), e is the dielectric constant of the semiconductor 0, and N is the n-type impurity concentration of the semiconductor. d is the layer thickness of the semiconductor.

), the territory of this seed is depleted.

Therefore, the necessary and sufficient reason for the small layer (electron supply layer) in the electronic Japanese book is the sum of the thickness as the electron source and the thickness of the depletion layer.

The gate-source capacitance 008 is ε　・　5 00B: however, C is the dielectric constant of the semiconductor), S is the area of the gate), d is /l of semiconductor.

Therefore, in order to reduce the source-gate electrostatic response, it is sufficient to increase the thickness of the electron supply layer. For this purpose, it is effective to reduce the n-type impurity concentration, but since this lowers the transfer conductance, in the present invention, the electron supply layer is divided into two parts, and the electron supply layer is divided into two parts, and the electron supply layer is divided into two parts. The impurity concentration of the layer is made as high as 1018/cm3 or more, and the density is made as thin as 60(X) or less, while in the depleted region, the impurity concentration of 6 degrees is reduced to 10''/α3 or The gate dielectric strength is improved by reducing the gate dielectric strength to less than that, and at the same time, the cutoff frequency is improved by reducing the gate-source capacitance aaB while maintaining high conductivity, resulting in an excellent high frequency. This is an actual look at its characteristics.

(5) Embodiment of the Invention A semiconductor device according to an embodiment of the invention will be further described below with reference to the drawings.

As an example in Figure 1, a semi-insulating gallium arsenide (Ge, As) substrate l contains n-type impurities below 10147r+n3:
A gallium arsenide (nGaAs) layer 2 having a thickness of (, OQQ~4.ooo(X) is formed, and n
An electron supply layer 3 is formed of a type aluminum gallium arsenide (nA/GaAs) layer I), and this electron supply layer 3 is divided into three layers, and the bottom layer is an amplifier with a 1o14 /I Contains n-type impurities below 3 and has a thickness of 20~
Aluminum gallium 9 (
n-A/GaAs) layer 31〒AI), the intermediate layer is made of aluminum gallium hyaluronan with a high concentration of 1.0187 (M, 3 or more) containing n-type impurities and a fraction of ho(X) or less. J (n”A/GaAs) N32〒AI), the top layer is an aluminum gallium arsenide (nA/GaAs) layer 33 whose top layer contains n-type impurities at a ratio of about 1017/σ3 and has an I height of 500-700 (X) On top of that is a Schottkycate electrode 4 and a highly concentrated n-type gallium arsenide (nGaA).
e) an electrode contact layer consisting of layer 5 is formed;
, a semiconductor device in which a drain electrode 6 and a drain electrode 7 are formed on the electrode contact layer 5 will be described.

Among the three layers constituting the electron supply layer 3, the undoped layer 3
1 has a function of preventing ion scattering and is not the gist of the present invention. However, due to n-type impurities diffusing from the adjacent layer, n-
It has become a type. Next, the high concentration n-type layer 32 is related to the gist of the present invention and satisfies the requirements for generating a two-dimensional electron gas having a surface density of about 1 g+1/cm2 or more, which is necessary and sufficient as a conductive medium of a semiconductor device. However, its thickness is extremely thin. Thirdly, the n-type RF433 in the uppermost layer satisfies the necessary and sufficient requirements to allow the formation of a depletion layer under the gate electrode, and is not buried more than necessary.

Therefore, the thickness of the electron supply layer 3 is sufficiently thin, the gate-source capacitance is sufficiently low, the cut-off frequency is increased, and the high frequency characteristics are improved.

Furthermore, since the impurity concentration of this n-type layer 33 is moderately low, the gate-source dielectric strength is also improved.

Referring to FIG. 2, the steps for manufacturing the semiconductor device shown in FIG. 1 will be explained below.

101 on a semi-insulating gallium arsenide (GaAs) substrate 1
Contains n-type impurities below 47cm' 3.000-4.
Gallium arsenide (nGs) with a thickness of
Aθ) layer 2 (!l-, amplifier with a value of 20 to 60
Aluminum gallium arsenide (nA/G
a, As ) layer 31 and It)"/lv3 or on it D?IA e contains n-type impurities and has a thickness of 6n [
Aluminum gallium arsenide (n+A/G
aAR) layer 32 and n-type impurity layer 9
Aluminum gallium arsenide (nA/GaAs) with ~5nn-7on (X) $33 and 2
Gallium arsenide (contains n-type impurities with a high degree of n of about ×1018/cm3) and has a mass of 500 to 1.000[s].
nGaAs) $5 is subsequently formed. This step is conveniently performed using molecular beam growth. As stated above, 1ω31 is n- due to the spread from neighboring stations.
It has become a type.

The layer 5 is a layer for lowering the contact resistance of the source electrode and the drain electrode, and is not the gist of the present invention.

Referring to FIG. 3, a part of the gallium arsenide (nGaAB) F 5 is selectively etched away to form a gate forming region 41 . This process uses photolithography method and HF:F!
This can be done by a wet etching method using 20□''20=2:16:500 as an etchant.

Referring to FIG. 4, after forming an aluminum (At) film, the gate 4 is formed by removing the aluminum (At) film in areas other than the gate. This step can be performed using a sputtering method, a photolithography method, and a wet etching method.

See Figure 1 (re-reference) Nothing other than the source/drain region/Cyst film (not shown).

) to form an AuGe/Au film, and then remove the resist film to form a source electrode 6 and a drain electrode 7. Thereafter, heat treatment is performed at 450 ('O) PI 4 degrees to alloy the lower regions of the source electrode 6 and drain electrode 7, thereby completing the semiconductor device.

In order to reduce the contact resistance of the source electrode and the drain electrode, it is simple and effective to gradually lower the aluminum mixed crystal ratio of the layer 33 and keep it in contact with gallium arsenide (Ga, As) in the upper part of the layer. be.

In the above embodiment, a high electron mobility transistor made of a combination of gallium arsenide (GaAs) and aluminum gallium arsenide ((AZGaA8) is described, but this is just an example). It is not limited. Further, in the above embodiments, the gate electrode is provided on the electron supply layer, but there are other examples, and the opposite layer structure may also be used. Furthermore, the gate electrode is not limited to the Schottky type, but also the MiS type and the junction type↑.
It suffices if the structure is such that a relatively fine concentration layer at the lower end of vN can be depleted.

(6) More than the effects of the invention 1) According to the present invention, the gate-source capacitance is small, the cut-off wave number is high, the high-frequency characteristics are excellent), and the gate dielectric strength is historically large. High electron mobility transistors with Schottky electrodes can be provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a semiconductor device (high electron mobility transistor) according to an embodiment of the present invention, and FIGS. 2 to 4 are sectional views 1 showing the manufacturing process thereof. 1...Substrate (GaAs), 2-n-type gallium arsenide (
3... electron supply layer, 31... undoped aluminum gallium arsenide (n-A/GaAs) layer, 3... electron supply layer, 31... undoped aluminum gallium arsenide (n-A/GaAs
s) Ffjj% 32-n'' aluminum gallium arsenide (n+A/GaAs) layer, 33...n aluminum gallium arsenide (nA/GaAs) layer, 4...Shirotki gate electrode, 41...gate formation region, 5,...n
gallium arsenide (nGaAs) layer, 6... source electrode,
7...P rain electric shuttle. Opening date U39-124769 (5) Figure 4

Claims (2)

[Claims] (1) A conductive medium is a group of electrons (two-dimensional electron gas) that stays near the interface of a double layer formed on a semi-insulating semiconductor substrate of two types of semiconductors with different electron affinities. The impedance of the conductive path constituted by the rod body is controlled by a control electrode provided on either of the semiconductor double layers, and the conductive path is formed by a pair of input wires provided with the control electrode in between. In the # conductor device connected to the output electrode, the layer with a low electron affinity among the conductor layers constituting the semiconductor double layer is further divided into two layers (I), which are in contact with the layer with a high electron affinity. A bioconductor device characterized in that the layer containing n-type impurities is a thin layer containing a high concentration of n-type impurities, and the layer that is not in contact with the layer having a high electron affinity is depleted under the control electrode. (2) The semiconductor device according to claim 1, wherein the leg plate and the layer having a high electron affinity are gallium arsenide (a) (a), the electron Yl - a layer with a low interest rate) J aluminum gallium arsenide. .